The Korean War, 1950-53, was a result of the division of Korea into North and South at the end of World War II. North Korea, supported by China, invaded South Korea, who were assisted by the USA in repelling the invasion.
America was involved in the crises of the Straits of Taiwan, conflicts which took place between China and Taiwan in 1954-55, 1958 and 1995-6, over Taiwan’s political status as part of the Republic of China or an independent country.
The Gulf War, the first war between America (and UN forces) and Iraq between 1990 and 1991, resulted from Iraq's invasion of Kuwait, and preceded the second invasion of Iraq in 2003.
America invaded Afghanistan as a direct response to the 9/11 attack – part of the USA’s ‘War on Terror’ (see bookmark for p.106).